Japanese Laid-open Patent Publication 2005-103623 discloses a wire drawing machine of a non-slip type using an unwinder for unwinding a metal wire to be drawn, a winder for winding the metal wire, and a wire drawing unit for drawing the metal wire. The wire drawing unit is formed of a capstan for drawing (or moving) the metal wire without slip, a dancer roller for applying back tension to the metal wire, and a wire drawing die for reducing the wire diameter. A plurality of such wire drawing units are connected in series between the unwinder and the winder. On the other hand, Japanese Laid-open Patent Publication Hei 10-180342 discloses a wire drawing machine to reduce its size, in which a wire to be drawn is sequentially wound around multiple capstans arranged in series and is transported therethrough, and is also allowed to pass through wire drawing dies placed between adjacent ones of the capstans, so as to draw and reduce the diameter of the wire sequentially through the dies. The capstans are sequentially placed in a zigzag arrangement in the transport direction of the wire so as to form multiple sets of capstans, each set of which consists of three adjacent capstans. Further, a single transmission gear is placed in each set of capstans so that the three capstans in each set are mutually rotated.
However, the conventional wire drawing machines have problems. For example, in the wire drawing machine of Japanese Laid-open Patent Publication 2005-103623, the dancer roller of each wire drawing unit for the application of tension is supported by an end of a dancer arm and driven to pivot about the other end of the dancer arm as a fulcrum. In the wire drawing unit, the wire (to be drawn) having passed the dancer roller is not directly inserted into the wire drawing die, but is required to pass an input guide roller so as to reverse the transport direction of the wire before being inserted into the wire drawing die. Furthermore, the pivot fulcrum of the dancer arm is distant from the wire drawing die in a direction substantially perpendicular to the direction of wire drawing of the wire drawing die, causing the occupying space of the wire drawing unit to be large. As a result, the wire drawing machine using the wire drawing unit or a plurality of such wire drawing units connected to each other becomes large in size. There is a possibility for the wire drawing machine with the multiple connected wire drawing units to be very long in the direction of the connection.
Besides, the pulling or drawing force of a capstan to pull a wire depends on a winding or wrap angle of the wire on the capstan. In the wire drawing machine of Japanese Laid-open Patent Publication 2005-103623, the winding angle of the wire on the capstan is small, and is at most 180 degrees. (Refer to the capstan 57 in FIG. 1 therein). Accordingly, the pulling force of the capstan to pull the wire therein is smaller to cause less stable wire transport than in the case where the wire is wound around the capstan multiple times.
On the other hand, in the wire drawing machine of Japanese Laid-open Patent Publication Hei 10-180342, one wire drawing die (D1) is placed between two capstans (K1, K2) in each set of three capstans to cause the two capstans to have different rotation numbers so as to generate a pulling force to pull the wire. Thus, it is required to finely control the rotation numbers of the two capstans. However, such fine control is difficult because the wire drawing machine has multiple sets of capstans, each set of which has three adjacent capstans. An insufficiently fine control is likely to cause slippage between the wire and the capstans, which in turn damages and strains the wire, and is very likely to cause gears for driving the capstans to make noise during high speed rotation.
The wire drawing machine of Japanese Laid-open Patent Publication Hei 10-180342 further describes a proposal to arrange two rows (upper and lower) of wire drawing units, each unit consisting of capstans and wire drawing dies, allowing a shorter length of the total connected wire drawing units than a single row arrangement. However, in order to place a wire over and between the wire drawing units in the upper row, the wire drawing units in the lower row are likely to hinder and make difficult the operation of placing the wire over and between the wire drawing units. In addition, the arrangement of this wire drawing machine requires that a wire supply unit for supplying the wire and a wire receiving or winding unit for receiving the diameter-reduced wire be positioned at both ends of the total connected wire drawing units, which are apart from each other in the direction of the connection of the wire drawing units. This causes the size of the wire drawing machine in the direction of the connection of the wire drawing units to be thereby larger.